The naturalistic fallacy is the erroneous belief that what is natural is morally acceptable. Two studies assessed whether people commit the naturalistic fallacy by testing whether genetic explanations for killing and male promiscuity, as compared to experiential explanations (i.e., learning/“nurture” explanations) increase acceptance of these behaviors. In Study 1, participants who read a genetic explanation for why people kill bugs viewed bug killing as more morally acceptable than participants who read an experiential explanation, although they did not reliably kill more bugs. In Study 2, men who read a genetic explanation for why men are more promiscuous than women reported decreased interest in long-term romantic commitment compared with men who read experiential explanations and women who read either explanation.